JMIR Publications

ABSTRACT

Background:

There is evidence that physical activity (PA) during childhood and adolescence is crucial, as it usually results in adequate PA levels in adulthood. Given the ubiquitous use of smartphones by adolescents, these devices may offer feasible means to reach young populations and deliver an intervention aiming to increase PA participation and decrease sedentary time. To date, very few studies have reported smartphone-based interventions promoting PA for the adolescent age group. In addition, the majority of available fitness apps do not include the latest evidence-based content.

Objective:

This study describes a systematic development of a behavior change, theory-based Mobile Application for Physical Activity (MAPA) intervention with personalized prompts for adolescents aged 16-18. The MAPA within-subject trial results are reported to provide first evidence of the general effectiveness of the intervention based on step count, sedentary time and MVPA minutes outcomes. The effectiveness of intervention component (personalized PA prompt) was also assessed.

Methods:

A 4-week within-subject trial with 18 healthy adolescents aged 16-18 years was carried out (mean age 16.33 years, SD=0.57). After the initial baseline week, participants used the MAPA intervention (Fitbit fitness tracker + app), that included a daily personalized PA prompt delivered via a pop-up notification. A paired t-test was performed to assess the general effectiveness of the MAPA intervention. Change point analysis was performed to assess the effectiveness of a personalized PA prompt 30 and 60 minutes after prompt delivery.

Results:

Overall, the results showed that the MAPA smartphone-based intervention produced significant reductions in sedentary time in adolescents during the first week of the trial (t(17)=-1.79, P=.04, bootstrapped P=.02). This trend, while remaining positive, diminished over time. Our findings indicate that there was no effect of the intervention on MET-based MVPA minutes, although the descriptive increase may give reason for further investigation. Although the results suggested no overall change in heart rate based MVPA minutes, the results from the change point analyses suggest that the personalized PA prompts significantly increased HR per minute (bpm) during the second week of the study (t(16)=1.84, P=.04, bootstrapped P=.04). There were no significant increases in participants’ overall step count; however, the personalized PA prompts resulted in a marginally significant increased step counts per minute in the second week of the study (t(17)= 1.35, P=.09, bootstrapped P=.05).

Conclusions:

The results of the trial provide preliminary evidence for the benefit of the MAPA intervention for modest yet significant reductions in participants’ sedentary time and beneficial role of personalized PA prompts. The current results also provide further evidence for the benefit and relative efficacy of personalized activity suggestions for inclusion in smartphone-based PA interventions. This study also provides an example on how to guide development of subsequent smartphone-based mHealth PA interventions in adolescents.